Beta plus decay: mass balance?


by Chem.Stud.
Tags: balance, beta, decay, mass
Chem.Stud.
Chem.Stud. is offline
#1
Aug13-13, 09:49 AM
P: 25
Hi:

I am taking a radiochemistry class, and I am confused by beta plus decay.

(1) p --> n + positron + electron-neutrino

The mass of a proton is less than the mass of a neutron. In addition, the neutrino has mass as does the positron.

(2) E = mc2

There must be come sort of balance, must there not? Mass cannot be created unless energy is consumed. So where does the nuclei get the energy from to convert a single proton into three different particles, one of which has a larger mass than the proton itself?

I hope I have made my confusion understandable. Also, my macbook would not let me use the greek characters or sub- and superscript.

Sincerely,
Anders
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SteamKing
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#2
Aug13-13, 10:13 AM
HW Helper
Thanks
P: 5,526
The beta-plus decay cannot occur in a single proton due to the need for energy to be supplied from some external source.

See: http://en.wikipedia.org/wiki/Beta_decay

In heavier nuclei, beta-plus decay can occur if the original nucleus has a higher binding energy than the nucleus which remains after the emission of the beta-plus particle.
Chem.Stud.
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#3
Aug13-13, 10:17 AM
P: 25
Ahh, that makes sense. Thank you for your help.


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